In a standard procedure for correcting a bite articulation defect in a dentate human jaw, impressions are taken of the maxilla and mandible, that is the upper and lower jaws, and positive models are prepared. Each model has portions corresponding not only to the front incisor, canine, and side molar regions of the patient's teeth, but also portions corresponding to the maxillary and mandibular tuberosities, that is the bony protuberances behind the third molars. A calibration plate is then used to work on the models thus produced in order to reset the so-called articulation or chewing plane.
An articulation defect is defined relative to this joint plane which itself is defined in the front by the lip line of the patient and in the rear by the jaw joint. This joint plane should be parallel to a plane defined by the centers of the ear holes in the rear and the bottom edges of the sides of the nose in the front.
Misalignments of the joint plane can result from teeth having been removed from the upper or lower jaws and the teeth in the opposing jaw shifting complementarily out. In the long run such a joint misalignment can result in considerable problems. Thus it is standard to fit crowns or bridges to patients who have or might develop such a joint-plane misalignment.
Normally the existence of a joint-plane misalignment is determined by visual examination of the model. It is also known to use a so-called articulator in which the model is mounted to try out solutions to the joint problem. Calibration plates are used which follow the uneven contours defined by the prominences of the teeth of the model.
The known method which uses an articulator nonetheless makes it very difficult to transfer any measurements to the patient accurately. Due to the inability to transfer these measurements to the natural teeth of the patient it is relatively difficult to guarantee good long-term results. This is particularly true when the patient is being fitted with a bridge, crown, or the like and it is necessary to determine whether there is any articulation defect and correct it. Typically marking paper is used to leave traces where the teeth meet, but this procedure is not highly accurate.